4,6-dichloro-5-fluoropyrimidine is an intermediate which can be used, for example, for preparing crop protection agents and dyes.
A process for preparing 4,6-dichloro-5-fluoropyrimidine has already been described In DE-A1-197 10609.
In this process, 4,6-dihydroxy-5-fluoropyrimidine is admixed with phosphorus oxychloride and dimethylaniline as base. For work-up, firstly the excess phosphorus oxychloride is distilled off and the residue is subjected to vacuum distillation. This process has the disadvantage that a relatively large amount of base is employed, and that the base can be recovered and re-used only at great cost. Moreover, during the aqueous work-up of the distillation residue, large amounts of wastewater with a high phosphate content are formed. Work-up on an industrial scale is therefore very complicated.
The preparation of 4,6-dichloropyrimidine is described in DE-A1-196 42 533 and DE-A1-195 31 299.
A process for preparing 4,6-dihydroxy-5-fluoropyrimidine is described in JP-A2-61 205 262. In this process, the condensing agent used is formamidine hydrochloride, which is a relatively expensive and highly hygroscopic condensing agent. Accordingly, this process is no alternative for industrial production.
Processes for preparing 4,6-dihydroxypyrimidine derivatives have likewise already been described (cf. WO-A1-94/44327, DE-A1-43 23 180, U.S. Pat. No. 847 139).